What not to eat when you're pregnant

There are certain foods that you should avoid — or at least exercise caution about — when you're an expectant mother.

Some women think it's OK to have an occasional glass of wine during pregnancy. Others abstain completely.
(Photo: ArtTim/Shutterstock)

Let’s face it; pregnancy is a big deal.

It’s one of the most life-changing events in a woman’s life, and often one of the most stressful. As such, it’s easy to get worked up about how to “do pregnancy right.” And it’s particularly easy to focus on all the things that can go wrong.

As a registered dietitian specializing in maternal, infant and pediatric nutrition, one of the first questions I often get from pregnant clients is about avoidance:

“What can’t I eat? ”

As a general rule, I don’t like to offer too many prohibitions. I prefer to focus clients on the positive aspects of pregnancy nutrition – highlighting the importance of a diverse, healthful range of whole foods (accompanied, of course, by the occasional indulgent treat). But there are certain foods and food groups that are worth exercising caution over and/or avoiding all together.

Here are some of the key categories.

Fish high in mercury

It’s important to remember that, in general, fish is good.

Fish and fish oils are considered the best sources of omega-3s, a family of polyunsaturated fatty acids that play a central role in both the healthy development of a baby and a healthy pregnancy itself. Studies have linked adequate omega-3 intake to neurological and visual development of the baby, reduced allergies and nervous system development. Omega-3s may also reduce risk of preterm labor, pre-eclampsia and post-natal depression.

However, some fish are contaminated with high levels of mercury, and mercury can effect brain development and the nervous system — some of the very same developmental processes that omega-3s are supposed to protect.

To maintain a safe fish intake and keep your omega-3s at a healthy level, eat fish considered low in mercury at least twice a week and/or supplement your diet with a good quality, purified fish oil. Fish to avoid due to extremely high levels of contamination include swordfish, king mackerel, shark, tilefish and bigeye or Ahi tuna. This second category of fish is considered best to eat in moderation, for example sea bass, bluefish, grouper, Spanish mackerel and some tunas like yellowfin and white albacore. These can be eaten up to three times a month without risk of over contamination. It’s best, however, to eat the majority of your fish intake from the group of species considered the lowest risk of contamination — these include crab, flounder, anchovies, haddock, salmon, tilapia, plaice and sole. For an exhaustive list of different mercury levels in fish, check out the American Pregnancy Associations guide to mercury in fish.

It’s worth remembering too, of course, that many fish are endangered and/or overfished. Check out the Monterey Bay Aquarium’s guide to sustainable seafood for more on which species can be eaten without fear of overfishing.

Caffeine

OK, coffee isn’t technically a food. But for those of us who already have kids, it can definitely be a fuel.

However, caffeine can raise the heartbeat and blood pressure of the baby. A heavy intake of four or more cups a day has been linked to an increased risk of miscarriage. That doesn’t mean you have to go without entirely because you are pregnant, but moderation is definitely called for. About one small cup of coffee or tea (not a 20-ounce mug!) is absolutely fine, and shouldn’t pose any risk to your pregnancy.

Soft cheeses and luncheon meats

Listeria is definitely a cause for concern in pregnancy. A bacteria that is found in both water and soil, listeria monocytogenes can be found in uncooked meats, vegetables and unpasteurized cheeses. Pregnant women are about 20 times more likely to become infected than the general population, and an infection can cause miscarriage, premature delivery or stillbirth.

Because listeria is killed by cooking and pasteurization, it’s recommended that pregnant women avoid raw milk, soft and unpasteurized cheeses like Feta, brie or camembert. Pates, smoked seafood, sushi, as well as hot dogs and lunch meat — unless heated thoroughly — should also be avoided. All vegetables should be washed carefully before preparation, and it’s important to keep your fridge clean and wash hands regularly, especially during food preparation.

Alcohol

It’s well known that heavy drinking during pregnancy can harm a baby’s development and even endanger the pregnancy. Nevertheless, anecdotal evidence suggests that many mothers these days will indulge in an occasional glass of wine or beer in the belief that it will not cause any harm.

The jury remains out on the safety of such habits.

Because researchers have yet to determine what a “safe” level of alcohol intake might be during pregnancy (if a “safe” level exists at all), the official advice of most medical and nutrition authorities remains to avoid alcohol all together during pregnancy, and certainly to avoid regular or heavy drinking.

Processed, junk foods

The old saying suggests that you are now “eating for two” — but this isn’t exactly true. Certainly your calorific needs are likely to increase significantly, but they will by no means double. On average, a pregnant woman needs about 300 more calories a day — the equivalent of half a sandwich or an extra bowl of cereal.

It can be tempting to turn to processed foods to fill the perceived calorie gap, whether it’s a fast-food hamburger, a candy bar or a bag of chips — and I’d never suggest we should deny ourselves an indulgence from time to time. (Yes, I ate ice cream during pregnancy!) But overindulging in processed foods is not going to do you or your baby any favors. Not only are many of these foods high in fat, sodium, sugar and other unhealthy additives, they also lack many of the vitamins, minerals, fiber and other nutrients that are so important for a healthy pregnancy.

Ultimately, the list of what not to eat is not as daunting as it might first seem.

In general, you should look to fill your body with healthy, nutritious whole foods as much as possible, such as whole grains, vegetables, fruits and proteins, and to supplement those whole foods with a few key supplements like DHA fish oils and a general pre-natal vitamin.

Jenni Grover MS RD LDN is a registered dietitian and co-founder of Realistic Nutrition Partners. She specializes in child, maternal and prenatal nutrition, with a focus on whole foods.